Here, beneath the imposing presence of the luxury Llao Llao Hotel, we boarded the first ferry, a large and comfortable catamaran, along with a couple of hundred other tourists. We were pleased to find out that most were only day trippers and would be returning to Bariloche that afternoon.

Only twenty people were heading on to Chile. Once away, the ferry quickly left the trappings of humanity behind as we headed down the long Brazo Blest, one of several long arms of Lago Nahuel Huapi.

Soon we were surrounded again by the landscapes of the National Park, the steep beech-lined lake shores merging into barren rocky ridges and peaks. It was hard to believe that only a few days earlier we had crossed these mountains on foot, looking down from above to the distant lake we were now on.

An hour later, we reached the end of the arm and Puerto Blest, a tiny settlement with one hotel and a cafeteria, but with an important place in history. It was here in 1922, that Nahuel Huapi was declared the first national park in Argentina. We had a two hour break here, time for an early lunch and a wander beneath the dark green canopy of the Valdivian Selva - the cold rainforest of the Andes.

A 3km bus ride from Puerto Blest brought us to the northern end of Lago Frias, the smallest and, perhaps because of this the most beautiful, of the three lakes crossed. It is a long and narrow lake, surrounded by high forest-clad walls; the pale green colour of the water giving away its origins in the glaciers of Monte Tronador.

We boarded a small barge-like ferry for the 20 minute journey down the length of the lake; soon after leaving port, the majestic white dome of Monte Tronador slowly appeared from behind the steep tree-lined slope of the Pared del Eco. The oohs and aaahs of the passengers were audible!

Kept amused by a continuous banter from our Chilean guide, the bus wound its way up a winding dirt road through the rain forest to cross the frontier at a low (1022m) pass and begin a long descent through the Perez Rosales National Park into Chile. We stopped briefly to get one last view of Tronador, looking back up a glacial valley from the Chilean side. It was sad to farewell the mountain that had been a constant presence for the last 10 days.

Soon the landscape opened out into a broad, flat valley, complete with braided river and steep mountain walls at its edge. Gradually farmlands began to appear and then the small settlement of Puella. Here we finally checked through Chilean customs and legally came to exist again. Some people take two days to do the crossing and break it by spending a night at one or other of the two hotels in Puella. I am glad that we didn't, as the place is overpriced and its setting is one of the least interesting of the trip.

From Puella, we boarded another large and comfortable catamaran, joined by lots of day-trippers from the Chilean side, for the 1 hour 40 minute journey down the deep blue-green coloured waters of Lago Todos los Santos. Again we were surrounded by tall tree-lined slopes beneath more barren rocky topped ridges. A couple of times the catamaran slowed down to allow new passengers to jump aboard from waiting fishing boats - no roads access these shores (the bus for the cross-frontier trip was brought in by barge).

The catamaran waiting beyond the reedbeds of the lake

Rounding one bend we were greeted with the sight of 2190m needle-like peak of Pico Puntiagado, an old volcanic plug, silhouetted against the sun. Rounding the next, the perfect 2652m snow-capped cone of distant Volcan Osorno welcomed us, softly backlit by the afternoon sun, and growing ever larger as we progressed up the long reach of the lake.

We had allowed ourselves a day's rest to roam the streets of Puerto Varas, explore the quaint shingle, weatherboard and galvanised iron architecture of its older houses and discover the strong German influence in this part of Chile, that makes "ja" an alternative to "si" and ensures a good supply of delicious kuchen and fine beers. The next stop would be Pucon and our 3-week intensive language course; our stomachs were already starting to tighten up a little.